[unreadable] Mycoplasma genitalium is a sexually transmitted microorganism recently identified from vaginal and cervical specimens using PCR technology, with a prevalence of 3-5%. This microbe is capable of invading the upper genital tract, and thus could plausibly be a cause of preterm birth and other pregnancy complications. However, the role of M. genitalium in preterm birth has not been systematically evaluated. We propose to examine the behavioral, infectious and reproductive correlates of M. genitalium infection among pregnant women in Lima, Peru. Our study design will take advantage of an on-going case-control study of infectious causes of preterm birth. 750 preterm cases and 750 controls will be selected from deliveries at the Instituto Materno Perinatal, a large tertiary referral center in Lima. Cervical swabs will be obtained after delivery for M. genitalium by PCR, as well as Chlamydia trachomatis and Neisseria gonorrhoeae. We will also evaluate vaginal Trichomonas and bacterial vaginosis. Demographic and behavioral information will be collected by standardized interview. The study has the following specific aims: 1. To examine the associations between M.genitalium infection and other STD with spontaneous preterm birth. 2. To examine sexual history and behavioral characteristics as risk factors for M. genitalium and other STD in pregnancy among Peruvian women. This research will be conducted primarily in Lima, Peru in collaboration with Pedro Garcia, MD, as an extension of NIH grant HD 41682. [unreadable] [unreadable] [unreadable]